A US police officer fatally shot a naked man who was chewing on the face of another man on a downtown causeway off-ramp, police and witnesses said.

The Miami Herald reports that gunshots were heard at about 2 PM on Saturday on the MacArthur Causeway off-ramp, which is near the newspaper's offices.

Witnesses said that a woman saw two men fighting and flagged down a police officer, who came upon a naked man mauling the other man.

The newspaper quoted witnesses as saying that the officer ordered the naked man to back away, and when he ignored the demand, the officer shot him.

Witnesses said that the naked man continued his attack after being shot once, and the officer shot him several more times.

Police said the other man was transported to Jackson Memorial Hospital Ryder Trauma Center. The newspaper said he had suffered critical injuries.

The police department confirmed in a news release that there was an officer-related shooting, but did not include many details provided by witnesses to the newspaper.

A police spokesman couldn't be reached for comment.

The police news release said the identities of the two men were not known.

A photograph posted on The Herald's website shows an officer standing watch on the ramp next to two police cruisers, with a body lying on a pedestrian walkway. Police requested the newspaper's video surveillance tapes.

The shooting and investigation tied up causeway traffic as crowds were arriving at South Beach for an annual hip-hop festival.

Javier Ortiz, a spokesman for the Fraternal Order of Police in Miami, said that based on information he's received, the officer who fired the shots “is a hero and saved a life.”